B. Forghani

A single scalar potential method for 3D magnetostatics using edge elements

It is demonstrated that it is possible to use a single, continuous, scalar potential to solve magnetostatic problems in three dimensions without the loss of accuracy associated with the reduced potential. This method makes use of tetrahedral edge elements and does not require the initial calculation of the field of the currents in the absence of magnetic materials. The method requires no numerical integration, has no restrictions on the current flow or the iron topology, and needs the solution of only one matrix problem. Results obtained by the method for translational and axisymmetric problems agree well with those computed by two-dimensional analysis with a vector potential. The method can be used to obtain accurate flux densities in both air and iron regions of three-dimensional problems. >

Effect of variation of B-H properties on loss and flux inside silicon steel lamination

The effect of the variation of B-H properties obtained by different means and data access modes under different exciting frequencies on iron loss and flux in GO silicon steel laminations is investigated, and the results of the numerical modeling is demonstrated on a benchmark model.

Adaptive improvement of magnetic fields using hierarchal tetrahedral finite elements

By using hierarchal tetrahedral finite elements, the polynomial order can be increased in poorly discretized regions of a mesh and an improved solution obtained for the magnetic field. An algorithm is proposed which estimates the error in each tetrahedron, by calculating the discontinuity of the normal component of flux density, and automatically adjusts the orders accordingly. Results are presented for an infinite sheet of copper carrying a time-harmonic current, an iron-core magnet excited by a DC coil, and the Bath Plate at 50 Hz. Setting all the elements to the highest order available gives the greatest accuracy, but almost the same accuracy can be obtained with fewer degrees of freedom after several adaptive steps. The cumulative CPU time of these steps is roughly the same as that of the highest-order solution, but significantly less memory is needed, and the adaptive route has the added advantage that it can be stopped at intermediate points if the computer resources run out. >

A scalar-vector method for 3D eddy current problems using edge elements

A finite-element method for eddy currents is described. By using fictitious currents in the conductors, this scalar-vector method is able to solve current-driven problems without cuts or extra circuit equations. The method uses what seems to be a minimum number of dependent variables: a vector in the conductors and a scalar elsewhere. Abrupt changes in permeability and conductivity are allowed. Results are given for the skin effect in an infinite slab of conductor; a conducting cylinder immersed in a uniform magnetic field; and the Bath cube. >

A Neural Network Model Of Magnetic Hysteresis For Computational Magnetics

A neural network to implement a hysteresis model for a magnetic material within a finite element program is described. It is shown that such a system can match the results produced by a Preisach model but the time overhead can be considerably reduced thus making feasible the solution of large problems involving hysteretic materials.

Effect of Excitation Patterns on Both Iron Loss and Flux in Solid and Laminated Steel Configurations

In this paper, the effect of different excitation patterns on both the iron loss and flux inside solid magnetic steel plates and laminated silicon steel sheets is investigated. Some practical approaches to nonlinear and anisotropic eddy-current problems under 3-D excitation conditions are proposed, in which the usual measured loss data is not adequate within the penetration depth where the eddy currents are induced by fluxes normal to the lamination. The benchmark results based on member models of Problem 21 with new extensions are presented to validate the proposal and to observe the electromagnetic behavior of the magnetic steel under different excitation patterns. The extensions to the benchmark Problem 21 are helpful for further Testing Electromagnetic Analysis Method (TEAM) activities.

Modeling magnetic materials using artificial neural networks

The accurate and effective modeling of magnetic materials is critical to the prediction of the performance of electromagnetic devices. The paper discusses the use of artificial neural networks as a uniform method for modeling the behavior of magnetic materials both isotropic and anisotropic, and with and without hysteresis.

3-D Finite Element Modeling and Validation of Power Frequency Multishielding Effect

The electromagnetic (EM) barrier, the magnetic (M) shunt and a combination of both are widely used in electrical devices in order to control stray fields and effectively reduce the power loss that may lead to hazardous local overheating. This paper focuses on the 3-D finite element modeling and validation of multishielding at power frequencies. The hybrid (M+EM) shielding behavior of the current magnetic shunt configuration is numerically and experimentally examined and is compared to other types. The leakage flux complementary-based measurement method of stray-field loss is also proposed and verified based on the benchmark shielding models.

DC current distributions and magnetic fields using the T-omega edge-element method

When steady currents flow in solid conductors, the current distributions are not known in advance, and a 3D finite-element analysis of the magnetostatic fields must also involve an analysis of the currents. To find the currents, either of two potentials can be used: the electric scalar potential or a vector potential T for the current density. The scalar potential has the disadvantage of producing a current density that is only approximately solenoidal, and is therefore incompatible with Amperes Law for the magnetic field. The vector potential gives solenoidal currents. It may conveniently be found by applying the T-/spl Omega/ edge element method, an existing method for eddy current problems, in one of two ways: setting the frequency so low that the DC solution is obtained; or solving first for T, then for /spl Omega/. Either way, both the current distribution and the magnetic field are obtained, and the solution is ideally suited for subsequent transient analysis. Results from three test problems confirm the validity of the method. >

Modeling of Magnetic Properties of GO Electrical Steel Based on Epstein Combination and Loss Data Weighted Processing

The extended modeling of the magnetic properties of grain oriented electrical steel is presented in this paper which is based on a set of standard and scaled-down Epstein frames and a proposed two-level weighted processing of Epstein data, including the mean magnetic path length, specific magnetization loss and exciting power. The effects of excitation frequency, strip angle, and ambient temperature on the results obtained from the Epstein frames are investigated. It is shown that using the proposed Epstein combination and the two-level weighted processing method is an efficient way of building a model for determining magnetic losses more realistically, hence, improving the value of Epstein strip measurement data.